Dispersible non-woven fabrics

ABSTRACT

The present invention relates to a dispersible nonwoven fabric comprising pulp and solvent spun cellulosic fibers, characterized in that the solvent spun cellulosic fibers are fibrillated. Furthermore the invention concerns the use of the fabric in dry wipes and wet wipes.

BACKGROUND OF THE INVENTION Field of the Invention

This invention is directed towards rapidly dispersible absorbentnonwoven fabrics and methods for making and using such products. Thisinvention is especially directed towards rapidly dispersible wet wipesthat are flushable through a standard toilet system and disintegrateinto easily dispersible fragments that biodegrade after disposal.

Not-woven textiles are defined with the terminology “nonwoven”. Thedefinition of nonwoven is described in the norm ISO 9092:1988. Absorbentnonwoven fabrics include materials such as dry wipes, wet wipes andcosmetic wipes and masks. They are also materials used in hygieneproducts like panty liners, sanitary napkins and incontinence products.The nonwoven fabrics used in these applications should fulfil therequirements of European Pharmacopoeia.

Disposable absorbent wipes such as toilet wet wipes offer high levels ofconvenience, comfort and efficacy that are greatly appreciated byconsumers. However, the popularity of these products has created a needregarding their disposal. General disposal methods used for wastematerials such bin disposal for subsequent incineration or landfill arenot convenient for the consumers, especially for using of toilet wetwipes. One of the alternative disposal methods is flushing the wet wipesdirectly into a conventional toilet. Flushing the product in the toilet,dispersing it by mechanical forces and finally biodegrading the materialin the sewage system is more convenient and discrete for the consumers.For this disposal method, the suitable material should maintain itsstructural integrity and strength for use, but also disintegrate readilywhen flushing into the toilet without causing any blockage in thepumping and drain systems.

Such products like toilet wipes are pre-moistened wipes. Therefore thenonwoven fabrics used for these applications should maintain theirmechanical strength and integrity in the wet state during storage andalso be biodegradable in the sewage system.

Flushable wet wipes are known for example from U.S. Pat. No. 5,629,081and EP 1 285 985 A1.

SUMMARY OF THE INVENTION

The object of the invention is to provide a dispersible nonwoven fabricwith good tensile strength but which disintegrate readily when flushed.

By the present invention there is provided a dispersible nonwoven fabriccomprising pulp and solvent spun cellulosic fibers characterized in thatthe solvent spun cellulosic fibers are fibrillated.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an unfibrillated Tencel by light microscope,

FIG. 2: shows an exemplary fibrillated Tencel by light microscope, and

FIG. 3: shows an exemplary fibrillated Tencel by scanning electronmicroscope.

DETAILED DESCRIPTION OF THE INVENTION

Especially suited as starting material for the fibrillated fibers aresolvent spun short cut cellulosic fibers with a length of 2 to 20 mm,preferably 3 to 12 mm, most preferably 4 to 10 mm The titer of thesolvent spun short cut fibers is 0.9 to 6.7 dtex, preferably 1.3 to 1.7dtex.

Preferably the solvent spun short cut fibers are present in thedispersible nonwoven fabric in an amount of 1 to 90 wt.-%, preferably 5to 40 wt.-%, most preferably 10 to 30 wt.-% based on the fabric.

A preferred solvent spun short cut fiber is a lyocell fiber, producedaccording to the Aminoxide-process, which is known e.g. from U.S. Pat.No. 4,246,221 (McCorsley). A suited solvent spun fiber is sold under thetrade name “Tencel”.

The dispersible nonwoven fabric has a weight of 30 to 100 g/m2,preferred of 40 to 60 g/m2 and a thickness of 0.1 to 0.7 mm.

The dispersible nonwoven fabric may comprise a dispersing aid in anamount of 0.1 to 1% wt.-%, preferably 0.5 to 1 wt.-% based on thefabric.

To increase the strength, optionally a binder is present in an amount of0.01 to 5 wt.-%, preferably 0.1 to 0.5 wt.-% based on the fabric,preferably in form of an acrylic resin or epichlorohydrin based resin,such as polyamide-polyamine-epichlorohydrin resins orpolyamide-epichlorohydrin resins. Other examples for suited binders arepolyethylenimine resins and aminoplast resins.

Any type of pulps are suited, especially softwood pulps, hardwood pulpsor a pulp made from plants like abaca or bamboo.

The dispersible nonwoven fabric according to the invention has a wettensile strength in machine direction of 2 to 20 N/5 cm, preferably 3 to13 N/5 cm and most preferably 3 to 7 N/5 cm based on a basis weight of60 g/m2 and in cross direction 1 to 10 N/5 cm, preferably 1 to 7 N/5 cmand most preferably 1 to 3 N/5 cm. The wet tensile strength has beenmeasured according to the EDANA Method WSP 110.4 (09) “Standard TestMethod for Breaking Force and Elongation of Nonwoven Materials (StripMethod)”.

One standardized test method for testing the properties of disposablewipes is known from “EDANA Guidance Document for Assessing theFlushability of Nonwoven Consumer Products”. This test is used to assessthe dispersibility or physical breakup of a flushable product during itstransport through household and municipal conveyance systems (e.g.,sewer pipe, pumps and lift stations). This test assesses the rate andextent of disintegration of a test material by turbulent water in arotating tube. Results from this test are used to evaluate thecompatibility of test materials with household and municipal wastewaterconveyance systems. The principle of the test method is that therotation of the tube is used to simulate the physical forces acting todisintegrate a product during passage through household sewage pumps andmunicipal conveyance systems. In this test the product is placed in aclear plastic tube containing 700 ml of tap water or raw wastewater,which is rotated end-over-end. After a specified number of cycles orrotations, the contents in the tube are passed through a series ofscreens. The various size fractions retained on the screens are weighed,and the rate and extent of disintegration determined.

The test material is disintegrating when at least 95% of the sizefractions pass a 12 mm screen and the residue is less than 5%.

The invention also concerns a process for the production of adispersible nonwoven fabric.

According to this wet lay process, pulp is dispersed in water and asolvent spun fiber is dispersed in water, either separately or togetheras a mixture. A dispersing aid such as CMC (Carboxymethyl cellulose) maybe added to improve dispersion quality. The dispersions are passedthrough a refiner either separately or are co-refined. The refiningenergy is from 20 to 400 kWh/t, prefer 40 to 150 kWh/t. A bindersolution may be added to the slurry. In the case of separate refining,the slurries are mixed to form an intimate blend to form one slurry. Theslurry is then wet-laid, e.g. on a papermaking machine, to form a sheet.The sheet then passes through a hydroentanglement process either on-lineor as a separate off-line process to form a fabric.

FIG. 1 shows an unfibrillated Tencel (light microscope). Fibrillation orrefining is a wet abrasion process that exposes and releases fibrilsemerging from the surface region of the filaments. As refiningprogresses, more fibrils are released from the filaments and thediameter of the residual filaments decreases (FIG. 2: light microscope,FIG. 3: scanning electron microscope).

In further steps the fabric is sliced into the appropriate format,folded and packed.

A treatment, preferably an impregnation, with a liquid or lotion can becarried out before packaging.

The invention is shown by the following examples:

EXAMPLE 1 AND EXAMPLE 2 (BOTH COMPARATIVE)

Wetlaid fabrics made of blends of woodpulp (Camfor pulp, a long fiberwoodpulp derived from spruce and pine, grown in British Columbia,Canada) with 15% Tencel short cut 1.7 dtex at 6 mm cut length(example 1) or 25% Tencel short cut 1.7 dtex at 6 mm cut length (example2) without any refining process and without additional of any additivesshowed a very good dispersibility according to the Tier 1 Test—FG511.2-Dispersability Tipping Tube Test of the “EDANA Guidance Documentfor Assessing the Flushability of Nonwoven Consumer Products”. Accordingto example 1, 100% of the disintegrated size fractions pass the 12 mm,the 6 mm and even the 3 mm screen, 21% retain and 79% passes the 1.5 mmscreen. But the fabrics did not show a high mechanical strength, both inmachine direction (MD) and cross direction (CD) as shown in Table 1.

TABLE 1 Tensile Strength Dispersibility of samples Fabric Thickness wetElongation Mass of each fraction in % in relation Fiber weight dry [N/5cm] wet [%] to dry mass Ex blends [g/m²] [mm] MD CD MD CD >12 mm >6mm >3 mm >1.5 mm <1.5 mm 1 15% 60 0.65 2.0 0.9 2.2 8 0 0 0 21 79 Tencel85% camfor pulp 2 25% 57 0.60 1.9 1.2 2.4 5 0 0 0 28 72 Tencel 75%camfor pulp

EXAMPLE 3, 4 AND 5

Blends of woodpulp (Camfor pulp) with 25% Tencel short cut 1.7 dtex at 6mm cut length including an addition of 0.5% CMC dispersing aid to theslurry. In these trials the pulp/Tencel blend was refined through 1×disc refiner and 4× conical refiners in series to levels of 40 kWh/t and60 kWh/t. Acrylic dry strength resin was added to the slurry at 1%(based on dry fiber weight). The fabrics were dispersible and thetensile strength of fabrics was improved (Table 2).

EXAMPLE 6

A blend of 80% woodpulp (Camfor pulp) with 20% Tencel short cut 1.7 dtexat 6 mm cut length was used to make wetlaid fabrics. Fibers were refinedto 100 kWh/t, 1% CMC (based on dry fiber weight) as dispersing aid wasadded and also 0.5% epichlorhydrin based wet strength resin (based ondry fiber weight) was added to increase the wet strength (Table 2). Thefabric was dispersible.

TABLE 2 Tensile Strength Dispersibility of samples Refining FabricThickness wet Elongation Mass of each fraction in % in Fiber Energyweight dry [N/5 cm] wet [%] relation to dry mass Ex blends (kWh/t)[g/m²] [mm] MD CD MD CD >12 mm >6 mm >3 mm >1.5 mm <1.5 mm 3 25% 40 590.28 3.6 1.3 4.2 39 0 0 0 55 45 Tencel 75% camfor pulp, 4 25% 60 56 0.253.3 1.5 5.0 33 0 0 0 53 47 Tencel 75% camfor pulp 5 25% 60 60 0.32 3.41.5 1.3 6.6 0 0 0 78 22 Tencel 75% camfor pulp + acrylic resin at 1% 620% 100 57 0.23 5.4 2.1 2.8 17 0 11 34 29 26 Tencel 80% camfor pulp +0.5% epichlorohydrin

EXAMPLE 7, 8, 9 AND 10

A blend of 75% woodpulp (Camfor) with 25% Tencel short cut 1.7 dtex at 6mm cut length was used to make wetlaid fabrics. Fibers were refined to80 kWh/t, 1% CMC as dispersing aid was added and also an epichlorhydrinbased wet strength resin was added to increase the wet strength atconcentrations of 0.05%, 0.10%, 0.15% and 0.20%. The results,demonstrated in Table 3, show that all samples were dispersible.

The fabric according to the invention can be used in dry wipes and wetwipes like toilette wipes, facial wipes, cosmetic wipes, baby wipes andsanitary wipes for cleaning and densification as well as in absorbenthygiene products such as panty liners, sanitary napkins and incontinencepads.

TABLE 3 Tensile Strength Dispersibility of samples Mass of RefiningFabric wet Elongation each fraction in % in relation to Fiber Energyweight Thickness [N/5 cm] wet [%] dry mass Ex blends (kWh/t) [g/m²]dry[mm] MD CD MD CD >12 mm >6 mm >3 mm >1.5 mm <1.5 mm 7 25% 80 58 0.593.7 1.6 11 50 0 0 1 64 35 Tencel 75% camfor pulp + 0.05% epichlorohydrinresin 8 As 80 60 0.53 4.1 1.9 11 50 0 0 4 63 33 Ex. 7 except with 0.10%epichlorohydrin resin 9 As Ex. 80 59 0.29 6.5 2.6 2.9 10 0 27 31 16 26 7except with 0.15% epichlorohydrin resin 10 As Ex. 80 59 0.42 5.5 2.2 8.828 0 2 30 36 32 7 except with 0.20% epichlorohydrin resin

1. A dispersible nonwoven fabric comprising pulp and solvent spuncellulosic fibers, wherein the solvent spun cellulosic fibers arefibrillated.
 2. The dispersible nonwoven fabric according to claim 1,wherein the fibrillated solvent spun cellulosic fibers are present in anamount of 1 to 90 wt.-% based on the fabric.
 3. The dispersible nonwovenfabric according to claim 1, wherein the fibrillated solvent spun fibersare lyocell fibers.
 4. The dispersible nonwoven fabric according toclaim 1, wherein the fabric has a weight of 30 to 100 g/m2, and athickness of 0.1 to 0.7 mm
 5. The dispersible nonwoven fabric accordingto claim 1, wherein the fabric comprises a dispersing aid in an amountof 0.1 to 1% wt.-% based on the fabric.
 6. The dispersible nonwovenfabric according to claim 1, wherein the fabric comprises a binder in anamount of 0.01 to 5 wt.-% based on the fabric.
 7. The dispersiblenonwoven fabric according to claim 6, wherein an acrylic resin orepichlorhydrin based wet strength resin is used as the binder.
 8. Thedispersible nonwoven fabric according to claim 1, wherein the pulp is apulp selected from the group consisting of a softwood pulp, a hardwoodpulp or a pulp made from plants like abaca or bamboo.
 9. The dispersiblenonwoven fabric according to claim 1, wherein the fabric is impregnatedwith a liquid or a lotion.
 10. The dispersible nonwoven fabric accordingto claim 1, wherein the impregnated fabric has a wet tensile strength inmachine direction of 2 to 20 N/5cm, based on a basis weight of 60 g/m²and in cross direction 1 to 10 N/5 cm.
 11. The dispersible nonwovenfabric according to claim 1, wherein the fabric is disintegrating underagitation in water according to Tier 1 Test FG 511.2-DispersabilityTipping Tube Test of the “EDANA Guidance Document for Assessing theFlushability of Nonwoven Consumer Products” where at least 95% of thedisintegrated size fractions pass a 12 mm screen.
 12. A process forproduction of a dispersible nonwoven fabric according to claim 1comprising the steps of a) Providing a dispersion of pulp and adispersion of solvent spun fiber in water either separately or togetheras a mixture, b1) Refining these dispersions separately and mixing theresulting slurries to an intimate blend to form a slurry, or, b2)Co-refining the mixture of pulp and solvent spun fiber to form a slurryc) Wet laying the slurry to form a sheet, and d) Hydroentanglement ofthe sheet to form a fabric.
 13. The process according to claim 12,wherein a dispersing agent is added to the dispersion in step a). 14.The process according to claim 12, wherein a binder is added in step b1)or b2).
 15. The process according to claim 12, wherein the refiningenergy is from 20 to 400 kWh/t.
 16. The process according to claim 12,wherein the solvent spun fibers are short cut fibers with a cut lengthof 2 to 20 mm and a titer of 0.9 to 6.7 dtex.
 17. The process accordingto claim 12, wherein the fabric is sliced, folded and packed.
 18. Theprocess according to claim 12, wherein the fabric is treated with aliquid or lotion before packaging.
 19. A product comprising a fabricaccording to claim 1.